Emergency medical care delivered to a patient occurs primarily in one of two settings: in hospitals by nurses and physicians, and in the field by trained emergency service providers, typically in the form of police officers, emergency medical technicians (EMTs), fire departments, paramedics or physicians in some cases. In the best medical systems, programs are put into place to assess current levels of care and to provide continuous quality-of-care improvements. Common measures of system effectiveness are endpoints such as survival, in the case of cardiac arrest, or improvement in health, in the case of non-terminal events. Additional interim measures are also important, however in determining areas for improvement in care; these data include response time and protocol adherence. While electronic patient charting software is now available, it is not uncommon to still see paper run reports being generated by emergency health care providers to record a patient's relevant personal information as well as the specifics of the vital signs of the patient and treatments delivered to the patient. The so-called run report or patient chart (RRPC) can subsequently be used by medical supervisory persons such as the Medical Director to determine statistical summaries of medical care performance. A common reporting format for care and outcomes, particularly in the pre-hospital setting, is the Utstein Style format as promulgated by the American Heart Association and other organizations. It is often the case that computers are used to enter data from paper run reports, the subsequent digital data then being processed to determine the aforementioned outcome and quality of care statistics as well as paper and electronic reports.
Data important to the determination of system effectiveness within the context, for instance, of treatment of cardiac arrest are critical time durations such as: time from 911 emergency phone call to arrival of the ambulance at the scene, time duration of transport from the scene to the hospital, time from arrival at the scene to delivery of the various medical therapies. The calculation of these durations involves multiple clock sources resident in the various diagnostic and therapeutic medical devices, the portable computer-based RRPC devices and the hospital and medical center-based base station computers.
Prior art has recognized the need for synchronization of more than one record stream to produce one integrated treatment history. E.g., U.S. Pat. Nos. 5,778,882, 6,095,985 and 6,282,441 provide for time-correlated medical event data on a personal digital assistant (PDA). Synchronization is performed based on time stamps for each record generated in the particular device; as a result, synchronization depends on how well the different clocks on the different devices are synchronized. U.S. Pat. Nos. 5,549,115 and 5,785,043 achieve an improvement in synchronization accuracy by storing the time-stamped event data in a removable memory device that has a built-in clock where the event times are correlated to the medical device clock time and the correlation is stored onto the memory device. When the data is downloaded from the memory device by an instrument such as a PDA or computer, the clock time as well as the correlation value are retrieved and when compared with the current time of the PDA clock, the record streams can be synchronized. U.S. Pat. No. 5,951,485 is very similar to U.S. Pat. No. 5,778,882 with the exception that it provides for more accurate time synchronization by communicating the current time of the device on which the data is stored to the PDA, which then determines a differential time discrepancy. The calculated time differential is used to more accurately correlate the events of the two devices.